This invention relates to a continuous wave radar altimeter.
In order to minimise the detectability of a radar altimeter, the transmitted power is kept to the minimum necessary to achieve an adequate signal-to-noise ratio, i.e. sufficient to obtain a reliable indication of height. However, it becomes necessary to increase the transmitted power temporarily when the signal-to-noise ratio drops, for example due to increases in flying height or to changes in the terrain. Previous methods of varying the power transmission have suffered from severe increases in detectability of the altimeter.